1. Field of the Invention
The present invention generally relates to a method for determining Stokes parameters.
2. Background Art
The Stokes method provides a seminal method for the determination of a state of polarization of a beam of light using measurable quantities. The Stokes method includes the process of measuring four intensities of the light beam. Each measurement corresponds to the intensity of the light beam after the light beam passes through each of four different filter system arrangements. The four Stokes parameters, by convention, are generally designated S0, S1, S2, and S3. The four Stokes parameters are derived from the four measured light beam intensities, and form a four-element column vector in four-dimensional mathematical space.
Since the discovery of the Stokes method in 1852, many conventional filter systems based on the Stokes method have been developed. Typically, in conventional approaches four separate, unique images are used to calculate the Stokes parameters for each element in a scene. A manually rotated retarder and a linear polarizer are used in conventional approaches to obtain the data used for determining the Stokes parameters.
However, the conventional approaches of using the Stokes parameters for acquiring polarization information from images have the deficiencies of sometimes having errors in temporal registration and in spatial registration. The temporal registration errors occur because of the capture time differential to generate separate images in conventional approaches. The capture time differential can affect polarization measurements that are taken outdoors when changing sun position, cloud position, and the like change the intensity or the polarization state of the light entering the filter system. Indoors (e.g., in a laboratory), temperature, atmospheric pressure, and density or concentration of variations associated with scene elements can change the polarization state of the light entering the filter system during the time duration used to record four separate images.
Spatial registration errors can occur when conventional approaches are used whenever the scene is imaged onto the image plane of the camera from different positions. For example, when four adjacent lenses are used to simultaneously image the scene on the image plane of the camera, each lens will obtain an image of the scene from a slightly different perspective. As such, the four images will be different, and spatial errors can occur.
Thus, there exists a need and an opportunity for an improved system and an improved method for the determination of polarization profiles of points in a scene from video frames. Such an improved system and method may overcome one or more of the deficiencies of the conventional approaches.